This invention relates to medical devices and particularly to a rotational atherectomy catheter device.
A variety of techniques and instruments have been developed for use in the removal or repair of obstructive material in arteries and other body passageways. A frequent objective of such techniques and instruments is the removal of atherosclerotic plaques in a patient""s arteries. Atherosclerosis is characterized by the buildup of fatty deposits (atheromas) in the intimal layer (under the endothelium of a patient""s blood vessels). Over time, what initially is deposited as relatively soft cholesterol-rich atheromatous material often hardens into a calcified atherosclerotic plaque. Such atheromas are often referred to as stenotic lesions or stenoses, the blocking material being referred to as stenotic material. If left untreated, such stenoses can so sufficiently reduce perfusion that angina, hypertension, myocardial infarction, strokes and the like may result.
Several kinds of atherectomy devices have been developed for attempting to remove some or all of such stenotic material. In one type of device, such as that shown in U.S. Pat. No. 5,092,873 (Simpson), a cylindrical housing, carried at the distal end of a catheter, has a portion of its side-wall cut out to form a window into which the atherosclerotic plaque can protrude when the device is positioned next to the plaque. An atherectomy blade, disposed within the housing, is then advanced the length of the housing to lance the portion of the atherosclerotic plaque that extends into the housing cavity. While such devices provide for directional control in selection of tissue to be excised, the length of the portion excised at each pass of the atherectomy blade is necessarily limited to the length of the cavity in the device. The length and relative rigidity of the housing limits the maneuverability and therefore also limits the utility of the device in narrow and tortuous arteries such as coronary arteries. Such devices are also generally limited to lateral cutting relative to the longitudinal axis of the device.
Another approach which solves some of the problems relating to removal of atherosclerotic plaque in narrow and tortuous passageways involves the use of an abrading device carried at the distal end of a flexible drive shaft. Examples of such devices are illustrated in U.S. Pat. No. 4,990,134 (Auth) and 5,314,438 (Shturman). In the Auth device, abrasive material such as diamond grit (diamond particles or dust) is deposited on a rotating burr carried at the distal end of a flexible drive shaft. In the Shturman device, a thin layer of abrasive particles is bonded directly to the wire turns of an enlarged diameter segment of the drive shaft. The abrading device in such systems is rotated at speeds up to 200,000 rpm or more, which, depending on the diameter of the abrading device utilized, can provide surface speeds of the abrasive particles in the range of 40 ft/sec. According to Auth, at surface speeds below 40 ft/sec his abrasive burr will remove hardened atherosclerotic materials but will not damage normal elastic soft tissue of the vessel wall. See, e.g., U.S. Pat. No. 4,990,134 at col. 3, lines 20-23.
However, not all atherosclerotic plaques are hardened, calcified atherosclerotic plaques. Moreover, the mechanical properties of soft plaques are very often quite close to the mechanical properties of the soft wall of the vessel. Thus, one cannot always rely entirely on the differential cutting properties of such abrasives to remove atherosclerotic material from an arterial wall, particularly where one is attempting to entirely remove all or almost all of the atherosclerotic material.
Moreover, a majority of atherosclerotic lesions are asymmetrical (i.e., the atherosclerotic plaque is thicker on one side of the artery than on the other). Since the stenotic material will be entirely removed on the thinner side of an eccentric lesion before it will be removed on the other, thicker side of the lesion, during removal of the remaining thicker portion of the atherosclerotic plaque the abrasive burr of the Auth device or the abrasive-coated enlarged diameter segment of the drive shaft of the Shturman device necessarily will be engaging healthy tissue on the side which has been cleared. Indeed, lateral pressure by such healthy tissue against the abrading device is required to keep the abrading device in contact with the remaining stenotic tissue on the opposite wall of the passageway. For stenotic lesions that are entirely on one side of an artery (a relatively frequent condition), this means that the healthy tissue across from the stenotic lesion will be exposed to and in contact with the abrading device for substantially the entire procedure. Moreover, pressure from that healthy tissue against the abrading device will be, in fact, the only pressure urging the abrading device against the atherosclerotic plaque. Under these conditions, a certain amount of damage to the healthy tissue is almost unavoidable, even though undesirable, and there is a clear risk of perforation or proliferative healing response. In some cases, this xe2x80x9chealthy tissuexe2x80x9d across from a stenotic lesion may itself be somewhat hardened (i.e., it has diminished elasticity); under such circumstances, the differential cutting phenomenon described by Auth will also be diminished, resulting in a risk that this xe2x80x9chealthyxe2x80x9d tissue may also be removed, potentially causing perforation.
Thus, notwithstanding the foregoing and other efforts to design a rotational atherectomy device, there remains a need for such a device which can advance through soft atheromas while providing minimal risk to the surrounding vessel wall. Preferably, the device also minimizes the risk of dislodging emboli, and provides the clinician with real-time feedback concerning the progress of the procedure.
In accordance with one aspect of the present invention, a rotational medical device is provided. The device comprises an elongate flexible tubular body, having a proximal end and a distal end with a rotatable element extending through the body. The body has a rotatable tip at its distal end which is connected to the rotatable element. A control is positioned on the proximal end of the body and an indicator is in electrical communication with the control. The indicator indicates resistance to rotation of either the rotatable element or rotatable tip.
In accordance with a further aspect of the present invention, a rotatable tip for use in an elongate flexible tubular catheter is provided for removing material from a vessel. The tip has a tip body having a proximal end and a distal end and a longitudinal axis of rotation extending between the two ends. A generally helical thread is provided on at least a distal portion of the tip body. Also, at least one radially outwardly extending cutter is provided on a proximal portion of the tip body.
A rotational medical device having an elongate flexible tubular body is provided in accordance with another aspect of the present invention. The tubular body has a proximal end and a distal end. A rotatable element is contained within and projecting distally from the flexible tubular body such that the rotatable element is either in sliding contact with or is spaced radially inward from the tubular body. An aspiration lumen extends within the tubular body between the interior surface of a wall of the tubular body and the exterior surface of the rotatable element. At the distal end of the tubular body, the present invention provides a rotatable tip which is connected to the rotatable element. The present invention also provides a control at the proximal end of the tubular body. The tubular body has a first cross-sectional area and the aspiration lumen has a second cross-sectional area wherein the cross-sectional area of the aspiration lumen is at least about 30% and preferably is as much as 50% or more of the cross-sectional area of the tubular body.
Preferably, a guidewire lumen extends throughout the length of the tubular body, or through at least a distal portion of the tubular body. The catheter may be used with either a conventional closed tip guidewire, or with a hollow guidewire having a distal opening thereon such as for infusion of therapeutic drugs, contrast media or other infusable material.
In accordance with another aspect of the present invention, a method of removing material from a patient is also provided. An elongate flexible tubular body, having a proximal end and a distal end, is provided. The tubular body has a rotatable tip on the distal end and a control on the proximal end. The rotatable tip is advanced to the location of the material to be removed. The control is manipulated to activate a vacuum through the tubular body. Then the control is manipulated to commence a rotation of the rotatable tip to remove the material from the patient.
In accordance with another aspect of the present invention, a rotational medical device is provided. The device has an elongate flexible tubular body, having a proximal end and a distal end with a rotatable element extending through the body. A rotatable tip is positioned at the distal end of the body and connected to the rotatable element. A control is positioned on the proximal end of the body and a guidewire lumen extends through the rotatable element.
In accordance with yet another aspect of the present invention a rotational atherectomy and aspiration catheter is provided for removing obstruction from a body vessel. The catheter comprises an elongate flexible tubular body, having a proximal end and a distal end and at least one lumen extending axially therethrough. A rotatable core extends through the lumen and a helical cutting tip is positioned on a distal end of the rotatable core. A vacuum source is coupled to the proximal end of the tubular body and a control is connected to the vacuum source that activates the vacuum source when the core is rotated.
A method of removing an obstruction from a body vessel is also provided in accordance with certain aspects of the present invention. The method comprises positioning a rotational atherectomy catheter at a treatment site in a body lumen and rotating a rotatable tip on the rotational atherectomy catheter to dislodge material in the body lumen. The method also involves applying a vacuum to the rotational atherectomy catheter to proximally withdraw material dislodged by the rotatable tip such that the vacuum is automatically applied in response to the step of rotating the rotatable tip.